Ultra-fast imaging

Ultra-fast imaging techniques are capable of acquiring a complete image in a time shorter than the spin-lattice relaxation time T. They can be used for imaging of dynamic 

Neglecting T relaxation during the experiment, the total transverse magnetization is given by the sum of the amplitudes Mxo of the individual FID signals. For a snapshot-FLASH image of N lines, this is 

Different contrast mechanisms are accessed by a clever modification of the FAST method. If adjacent pairs of rf pulses are identified as the pulses generating a Hahn echo, then the FID following the first pulse can be understood to be refocused by the second pulse to form a spin echo. In the echo maximum the next pulse is applied, so that the echo time t corresponds to twice the repetition time tR. By reordering the timing of 

13 [Man4] Principle of echo-planar imaging. Representation of the letter F by i discrete spin density and projections for three gradient directions. 

According to the convolution theorem (4.2.14), the Fourier transform S(oj) of the echo train is given by the product of the Fourier transform E ( ) of an echo e(f) and the Fourier transform F co) of the delta-comb function /(f). 

---

A.J. Sederman, M.D. Mantle, L.F. Gladden, Single exdtation multiple image RARE (SEMI-RARE), ultra-fast imaging of static and flowing systems. Journal of Magnetic Resonance, 2003, 161, 15-24. 

Three general ultra-fast sampling strategies are used Echo planar imaging... 

Bhattacharya P, Harris K, Lin AP, Mansson M, Norton VA, et al. 2005. Ultra-fast three dimensional imaging of hyperpolarized 13c in vivo. Magma 18 245-256. 

R 466 J. G. Kempf and J. P. Loria, Theory and Applications of Protein Dynamics from Solution NMR , Cell Biochem. Biophys., 2002,37,187 R467 E. Kennett and P. Kuchel, Redox Reactions and Electron Transfer Across the Red Cell Membrane , lUBMB Life, 2003,55, 375 R 468 R. G. Khalifah, Reflections on Edsall s Carbonic Anhydrase Paradoxes of an Ultra Fast Enzyme , Biophys. Chem., 2003,100,159 R 469 A. A. Khrapitchev and P. T. Callaghan, Spatial Dependence of Dispersion , Magn. Reson. Imaging, 2003, 21, 373 R 470 I. V. Khudyakov, N. Arsu, S. Jockusch and N. J. Turro, Magnetic and Spin Effects in the Photoinitiation of Polymerization , Des. Monomers Polym., 2003, 6, 91... 

MiiUer CR, Davidson JP, Dennis JS, Petmell PS, Gladden LP Real time measurement of bubbling phenomena in a 3-D gas-fluidized bed using ultra-fast magnetic resonance imaging, Phys Rev Lett 96 154—504, 2006. 

Muller CR, Davidson JF, Dennis JS, Fennell PS, Gladden LF Oscillations in gas-fluidized beds ultra-fast magnetic resonance imaging and pressure sensor measurements. Powder Technol 177 87-98, 2007. 

It should be noted here that the ultra thin-layer cells (UTLC) which result from the close approach of an STM tip to a conducting substrate may have important electroanalytical applications in studies other than STM imaging (64). This is because extremely large current densities should be attainable in such cells, and also because of the fast transit times (e.g., 50 nsec for d - 10 nm) for reactants across the cell. Thus, such UTLC s might facilitate the determination of fast heterogeneous rate constants or the study of reactive electrochemical intermediates (64). 

---